Pulse modulated microwave plasma etching

Abstract

The etching characteristics of silicon and silicon dioxide are studied in an anisotropic microwave plasma etching system using a variably pulsed microwave source. The pulse frequency, as well as the pulse duty cycle, of the microwave source can be varied. Etch characteristics being examined include etch rate, etch anisotropy, and etching selectivity between silicon and silicon dioxide. An attempt is being made to understand better the surface chemistry occurring during the plasma etching process. In conventional systems reaction products build up on the silicon or silicon dioxide surface during etching, and thus the etch rate slows as the thickness of the layer of reaction products increases. When the plasma discharge is pulsed, this layer can be modified or cleared away from the surface, allowing for improved etch characteristics. >